Lift gate for truck body



Sept. 2, 1958 D. H. ZWIGHT 2,850,186

LIFT 'GATE FOR TRUCK BODY Filed March 26, 1956 2 Sheets-Sheet l IN V ENTOR.

.Dan/Ie/ H Z 1449/72 410/ c. flaw D. H. ZWIGHT LIFT GATE FOR TRUCK BODYSept. 2, 1958 2 Sheets-Sheet 2 Filed March 26, 1956 INVENTOR. flan/2d19. Z nay/1f United States Patent i LIFT GATE FOR TRUCK BODY Daniel H.ZWight, Leavenworth, Wash.

Application March 26, 1956, Serial No. 573,717

6 Claims. c1. 'z14 7s This invention relates to a lift gate for the rearend of a truck body and an object of this invention is to provide aliftgate of this type which is electrically operated and which is simple inconstruction, eiiicient in operation and not expensive to manufacture. 7

Another object of this invention is -to provide electrically operatedlift gate mechanism which can be assembled as a unit ready forinstallation on the rear end of a truck body and which is adjustable tocompensate for variations in the width of truck bodies.

Another object is to provide a lift gate comprising a transverse supportattachable to the rear end of a truck body, two spaced apart uprightparallel guide members rigid with said support, two rolling beam typelift bars vertically movable in said guide members, two roller chainslying fiat against and secured to the frontfaces of the lift bars,sprocket pinions meshing with said roller chains and a deck pivotallyattached to the lower .end portions of the lift bars. I

Another object is to provide lift gate'mechanism in which a roller chainis applied to a lift member and meshes with a sprocket pinion .in such.a manner that the roller chain functions as a rack without passingaround the pinion or flexing or bending and atthesame time retains itsroller characteristics and serves as an anti-friction means facilitatingmovement of the liftbar in a guide member with a minimum amount offriction thus providing smoother and easier'lifting and lowering ofloads on a deck which is-secured to the lower end of the lift'bar. I

Another object is to provide lift gate means for the rear end of a truckbody in which ayertically movable deck is raised and lowered by ane'lectricmotor operating through self locking gear reduction meansthereby :providing accurate control of the vertical movement of the deckincluding the stopping and holding of the :deck at any desiredelevation.1

Other objects of the invention will be apparent-from the followingdescription taken in connection with .the accompanying drawings. I

Figure 1 is a side elevation showingtherear end of a truck equipped withmy lift gate, .the deck being in a lowered and horizontal position.

Fig. 2 is a detached assembly view in plan, with parts broken away,showing a bed-plate together with .upright guide members and bracketswhich form part of this'lift gate.

Fig. 3 is a fragmentary elevation looking in thedirection of broken line33 of Fig. 2.

Fig. 4 is a View partly in section and partly in elevatio looking inthedirection .of broken line 4-4 of Fig. 3.

Fig. '5 is a detached rear elevational viewof the lift gate mechanism,with parts broken away to reveal interior constructions, and showingadeck-in araised and oriented position which it would ordinarily occupywhen forming the tail gate closure means-for a truck body.

Fig. 6 is a vertical sectional view through an upright guide membershowing in elevation therein a movable e widths.

roller beam type lift bar having a deck attached to 2,850,186 PatentedSept. 2,1958

its lower end and having a roller chain lying flatly against and rigidlyattached to its front face with a sprocket pinion engaging the rollerchain. i e 1 Fig. 7 is a view in cross section on a larger scale thanFig. 16 looking in the direction 'of broken line 7- -7 of Fig. 6, partsbeing shown in plan.

Fig. 8 is a view partly in elevation and partly in cross section takensubstantially on brokenline 88 of Fig. 7. I

Fig. 9 is a'view in cross section, on a larger scale than Fig. 6, takensubstantially on broken line '9"9 of-Fig. 6. Fig. 10 is a view in crosssection, on a larger scale than Fig. 6 taken substantially on brokenline .10--10 of Fig. 6.

This electrically operated lift gate mechanism comprises two uprightspaced apart parallel tubular guide scription as applied to the guidemember 16 Will'apply equally well to guide member 15.

Each guide member 15 and'16 has a verticallyor longitudinally extendingstraight track 318 of :less :width .than

the guidemember secured to the inner side of its front wall. Also eachguide member has an inclined bottom end '17 which slopes downwardly fromtherear toward the front side of the guide member. The top end of eachguide member .15 and 16 has a rigidly attached cap 20 and a rubber shockpad 21 is disposed within each guide "member and-rests against the cap20.

The inner side plate of each guide member 15 and 16 terminates short ofthe lowerend of -theguide"member :toprovide clearance for partshereinafter described, see

Figs. 3,4 and 6. i

The bed plate means whichrigidly supports the two guide members 15 and.16. in spaced apart parallel upright 'relation at the rear end of thetruckbody 17, s'eeFigs.

2, .3 and 4, is as follows: A transverse angle bar 522 extends betweenand has its two ends rigidly secured to the two guide members 15 and 16.,Two corner gusset plates 22 are rigid with the angle bar 22. and? therespective guide members 15 and 16 and serve as trusses-and angle bracesto render the structure rigid. A flat bed .plate 23 overlaps and isrigidly secured to the angle'bar 22. The flat bed plate 23 rests uponand is securediby bolts 24 to the floor 25 of the truck body. The. endof: the bed plate 23 shown at the left in Figs- Z-and 3,has inwardlyextending slots 26 and is lapped byan adjust- .ment plate 27. The twoplates 23 and 27;.are adjustably .secured to each other and to the truckbed floor 25 :by

bolts 28. Thus the two bed plate members 23 :and 27 are relativelyadjustable to fit truck bodies of different .The extension plate'27 hasan upright angle bracket 29 rigidly connected with its outeredge and;extending upwardly therefrom. The angle bracket '29 is, secured to aside wall 30 of the truck body by suitable .means, such as bolts 31 anda backing plate32; The

outwardly extending flange of the angle bracket 29 is adjustablysecured,by bolts 33 operating in slots 34,"to a transversely extendingattachment plate '35 which vis rigid wit-hthe adjacent upright guidemember 15. Thus adjust- .ment of the bracket 29 to truck bodies ofvariable widths is providedand the bracket 29 is rigidly connected withthe -guide member 15 after this adjustment has 'been made but the guidemember 15 is not adjustablewith the bracket 29 and adjustment plate 27.The endportion ofthe flat bed plate 23'shown at the-right in Figs.

2. and 3 is provided with an upwardly extending'rigid bracket 36. Thebracket 36 is secured to a side wall I 31) of the truck body by suitablemeans such as bolts 31' and a backing plate 32. The bracket 36 has anoutwardly extending reversely bent portion 37 which is rigidly securedto the upright guide member 16. Preferably most of the parts of thisdevice which are per' manently rigidly secured together are welded. Thestructure just described provides a rigid assembly comprising theupright guides 15 and 16, cross bar 22, bed plate 23 and bracket 36 withplate 27 and bracket 29 forming an adjustable part of this assembly. Therigidly assembled parts insure proper spacing and support of the uprightguide members 15 and 16. The adjustable parts 27 and 29 adapt this liftgate structure to trucks having bodies of varying widths withinpredetermined limits.

Two rolling beam type lift bars 40 and 41 of I shaped cross section andof duplicate construction except that, in some respects they are rightand left, are longitudinally movably disposed within the respectiveguide members 15 and 16. Each lift bar, see bar 41, Figs. 1, and 6 to 10inclusive, has a piece of roller chain 42 of substantially the samelength as the lift bar placed flat against the forward face of the liftbar and secured to the lift bar. The roller chain 42 is taut from end toend and is supported against the lift bar so that it does not flex orbend. The edges of the links forming the chain 42 may be brazed orwelded to the lift bar throughout the entire length of the lift bar orapproximately six inches of each end portion of each chain 42 may bethus brazed or welded to the lift bar. The diameters of the rollers ofthe chain 42 are less than the width of the end portions of the links sothat the rollers do not contact the faces of the lift bars but saidrollers do roll on the tracks 18 and thus reduce friction and providesmoother operation in lifting and lowering loads.

Each lift bar 40 and 41 has a mounting block 38 rigidly secured to itstop end and each mounting block 38 carries a rotatively mountedanti-friction roller 39 which engages with and rolls on the insidesurface of the back wall of the guide member 15 or 16.

Two brackets, 43 and 44, Figs. 1, 5, 6 and 10, of duplicate constructionexcept that they are made right and left, are welded or otherwiserigidly secured to the lower end portions of the respective lift bars 40and 41 and extend rearwardly at right angles therefrom. Each of thesebrackets, see bracket 44 Fig. 10, has a thickened part 45 which fitsbetween the flanges of the lift member 41. An inwardly protrudingshouldered pin 46 extends through the thickened part 45 of each bracket43 and 44 and through the adjacent lift bar 40 or 41 and is welded tothe lift bar and to the bracket part 45. The inwardly directed endportion of each pin 46 is of reduced diam eter and is threaded toreceive a nut and forms a pivot stud for a lift deck as hereinafterdescribed. The rearwardly extending end portion of each bracket 43 and44 is provided with an inwardly directed shelf 47.

The combined tail gate and lift platform, herein referred to as thedeck, comprises two flat side bars 48 and 49 connected by cross bars 50,Fig. 5, and having a'metal top plate 51 secured thereto. Preferably theouter end of the plate 51 is sloped downwardly to facilitate handlingloads and articles thereover. The end portions of the flat side bars 48and 49 adjacent the lift bars 40 and 41 are pivotally mounted on thestud pins 46. This provides pivotal movement of the deck from agenerally horizontal position with the side bars resting on the shelves47 of the brackets 43 and 44 to an upright position in which the deck,when elevated, serves as a tail gate or closure member for the rear endof the truck body 17. The deck is locked in the upright elevatedposition in which it is shown in Fig. by two bolts 52 which have theirinner ends pivotally secured to a cross bar 53 and their outer endsslidably disposed in tubular sleeves 54. j

Preferably a spring 54' urges each bolt 52 outwardly. The cross bar 53is fulcrumed on a pivot 55 and has a handle 56 by which the bolts 52 maybe retracted. The outer ends of the bolts 52 can lock into suitableholes in the upright guide members 15 and 16 thus locking the deck in anupright raised position. Preferably two rearwardly projecting horizontalsupport pins 66, Fig. 2, are secured, one to the upright guide member 15and the other to the bracket part 37 and holes 67, Fig. 5, in the plate51 fit over these pins when the deck is in a raised and upright positionso that the pins 66 help to support the deck.

A shaft 57 extends crosswise of the rear end of the truck body 17 justbelow the level of the bottom 25 of said truck body and two sprocketpinions 58 are secured to this shaft 57 and extend through suitableopenings 58' in the front walls of the guide members 15 and 16 and meshwith the roller chains 42 on the forward faces of the lift bars 40 and41. Obviously rotation of the shaft 57 will move the two lift bars 40and 41 either up or down with the roller chains 42 functioning likeanti-friction racks. A bearing member 39 of sintered bronze is providedin each guide member 15 and 16 opposite to the pinion 58 to resist theseparation force due to this pinion.

Shaft mounts or bearings 59 and 60, Figs. 4 and 5, rotatively supportthe respective end portions of the shaft 57 and one end portion of saidshaft 57 extends into a gear housing 61 where further bearings areprovided and the shaft 57 is connected with suitable speed reductiongears. The speed reduction transmission means in housing 61 preferablyincludes self locking worm means. Since this transmission is ofconventional construction and easily obtainable on the market it is notdescribed in detail. A direct current motor 62, which can be energizedfrom the usual battery of the truck, is connected with the transmissionin housing 61 for driving the same. A switch box 63 containing thecontrol means for the motor 62 is mounted on a plate 64 which is securedto the guide member 16. The electrical control means in the switch box63 may be of conventional form and is not herein described in detail.The transmission housing 61 is secured by brackets 65 to the uprightguide member 16 and the motor 62 may be mounted on said housing 61. Thusall of the driving units are carried by the guide member 16 and areparts of the lift gate assembly and are mounted directly on the truck.

The deck 51 is shown substantially at ground level in Fig. 1 but theguide members 15 and 16 and lift members 40 and 41 are preferably longenough to permit lowering the deck several inches below the level of thesurface on which the truck rests. The deck can be raised at least highenough to bring it flush with the floor 25 of the truck body. When saiddeck is in a raised position and flush with the bed plate 23 loads maybe transferred smoothly and easily between the truck and the deck oversaid bed plate.

The roller chains 42 are secured to and lie flatly against the lift bars15 and 16 at all times and the rollers of these chains insure minimumfriction with the sprocket pinion 58. The chain rollers further bearagainst and have rolling contact with the racks 18 and the rollers 39 onthe upper ends of the lift bars maintain rolling contact with theopposite walls of the guide members 15 and 16. Thus the leverage exertedon the lift bars 15 and 16 by a load on the deck will be borne by thechain rollers and the rollers 39 and the friction incident to verticalmovement of the lift bars 40 and 41 in the guide members 15 and 16 willbe minimized.

The foregoing description and accompanying drawings clearly disclose apreferred embodiment of my invention but it will be understood thatchanges may be made within the scope of the following claims.

I claim:

1. In a lift gate for attachment to the body of a truck, an uprightguide member; a longitudinally extending track within said guide member;a lift bar longitudinally movable in said guide member; a roller chainsecured to and lying flat against one face of said lift bar andsupported against flexing throughout its entire length by said lift bar,said roller chain having rolling engagement with said track; a drivenpinion meshing with said roller chain longitudinally moving said liftbar in said guide member when it is rotated; and a lift deck pivotallyconnected with the lower end of said lift bar movable from a horizontalto an upright position and extending away from the side of the lift baropposite said roller chain when it is in a horizontal position.

2. In a lift gate for a truck body, an upright guide member ofapproximately rectangular hollow cross section; a rolling beam type liftbar of I shaped cross section longitudinally movable in said guidemember; an anti-friction roller rotatively mounted on the upper endportion of said lift bar and having rolling contact with one side ofsaid guide member; a roller chain lying flat against and rigidly securedto the face of said lift bar opposite the side at which said roller ismounted; a track in said guide member engaged by said roller chain; anda sprocket pinion engaging the side of said roller chain outwardly fromsaid lift bar, said anti-friction roller and said roller chain providingrolling contact of said lift bar with two opposed sides of said guidemember.

3. In a lift gate for a truck, two upright spaced apart parallel guidemembers secured to the rear end of the truck; a lift bar longitudinallymovable in each guide member; a roller chain lying flat against andfixedly secured to one face of each lift bar and supported againstflexing throughout its entire length by the lift bar; a transversedriven shaft extending across both of said lift bars; two sprocketpinions secured to said shaft and meshing with the sides of therespective roller chains outwardly from the lift bars; speed reductiongear means including a self locking worm connected with said shaft; anelectric motor having a driving connection with said speed reductiongear means; and a deck pivotally connected with the lower ends of saidlift bars.

4. In a lift gate for attachment to the rear end of a truck body, anormally horizontal bed plate resting on and attached to the floor ofthe truck body; an upright bracket rigid with one end portion of saidbed plate and attachable to the side of the truck body; another uprightbracket adjustably connected with the other end portion of the bed plateand attachable to the other side of the truck body and affordingadjustment to truck bodies of different widths; two upright spaced apartparallel guide members secured'to said bed plate; a lift bar movable ineach of said guide members; a roller chain lying flat against andfixedly secured to one face of each lift bar and inflexibly supportedthroughout its entire length by the lift bar; a driven shaft extendingcrosswise of said lift bars and said guide members; two sprocket pinionssecured to said shaft and meshing with the roller chains on therespective lift bars; and a deck pivotally connected with the lower endportions of the lift bars.

5. The apparatus as claimed in claim 4 in which the driving means forthe shaft comprises an electric motor connected with the shaft by aspeed reduction gear including a self locking worm and in which thespeed reduction gear and motor are both mounted on one of the uprightguide members providing a lift gate assembly in which all of the partsare attachable to and detachable from the truck body as a unit.

6. In a lift gate for attachment to the rear end of a truck body, across bar; a normally horizontal bed plate secured to said cross bar andresting on and attached to the floor of the truck body; a fixed uprightbracket rigid with one end portion of said bed plate and attachable toone side of the truck body; an adjustable upright bracket adjustablyconnected with the other end portion of the bed plate and attachable tothe other side of the truck body; an upright guide member secured to oneend of said cross bar and to said fixed bracket; another upright guidemember secured to said cross bar and said bed plate adjacent saidadjustable bracket, said cross bar and said bed plate supporting saidguide members in relatively fixed spaced apart parallel relation andsaid adjustable bracket providing adjustment to truck bodies of varyingwidths; a lift bar movable in each of said guide members; a roller chainlying flat against and fixedly secured to one face of each lift bar andsupported against flexing throughout its entire length by the lift bar;a driven shaft extending cross wise of said lift bars and said guidemembers; two sprocket pinions secured to said shaft and meshing with theroller chains on the respective lift bars; and a deck pivotallyconnected with the lower end portions of the lift bars.

References Cited in the file of this patent UNITED STATES PATENTS2,391,173 Loftus et a1. Dec. 18, 1945 2,405,054 Pringle July 30, 19462,553,156 Woodward May 15, 1951 2,581,333 Vawter Jan. 1, 1952 2,698,103Rostine Dec. 28, 1954 2,706,565 Krasno Apr. 19, 1955

